oce (version 0.9-18)

velocityStatistics: Report Statistics of adp or adv Velocities

Description

Report statistics of ADP or ADV velocities, such as means and variance ellipses.

Usage

velocityStatistics(x, control, ...)

Arguments

x

an ADV or ADP object.

control

an optional list used to specify more information. In this version, this is ignored for ADV objects. For ADP objects, if control$bin is an integer, it is taken as the bin to be selected (otherwise, an average across bins i

...

additional arguments that are used in the call to mean.

Value

• A list containing items the major and minor axes of the covariance ellipse (ellipseMajor and ellipseMinor), the angle of the major axis anticlockwise of the horizontal axis (ellipseAngle), and the x and y components of the mean velocity (uMean and vMean).

Details

This function has been tested on only a single file, and the data-scanning algorithm was based on visual inspection of that file. Whether it will work generally is an open question.

Examples

library(oce)
data(adp)
a <- velocityStatistics(adp)
print(a)
t <- seq(0, 2*pi, length.out=100)
theta <- a$ellipseAngle * pi / 180
y <- a$ellipseMajor * cos(t) * sin(theta) + a$ellipseMinor * sin(t) * cos(theta)
x <- a$ellipseMajor * cos(t) * cos(theta) - a$ellipseMinor * sin(t) * sin(theta)
plot(adp, which="uv+ellipse+arrow")
lines(x, y, col='blue', lty="dashed", lwd=5)
arrows(0, 0, a$uMean, a$vMean, lwd=5, length=1/10, col='blue', lty="dashed")